1. Field of the Invention
The present invention incorporates by reference U.S. Pat. No. 4,950,913 issued Aug. 21, 1990. This patent relates to a monitoring device for monitoring a system battery powering an external device, such as a two-way radio, when the motor is not running. During this time, the battery is discharged by the external device. A timer in the monitoring device allows the radio to run for a pre-set time. U.S. Pat. No. 4,950,913 also includes a separate voltage detector which will override the timer and shut off the radio upon the detection of a low battery voltage as well as a vibration detector which detects vibrations from the engine to reset the timer whenever the motor is started.
The battery of the automobile powers CBs, AM/FM radios, two-way radios, cellular phones, radar devices and other electronic communication systems. Now, with sophisticated technology, many automobile electronic components use mobile data terminals and other memory intensive products. People who use memory intensive communication systems in their cars or trucks need to leave the systems on when the vehicle is unattended, and not worry about draining the battery. With modern technology, this can include waiting for a page from a control center, status reporting or in-coming data. The most common reasons, however, are the inconvenience of manually turning the system off each time one leaves the vehicle, and connecting numerous electronic equipment to the battery which will drain the car battery.
U.S. Pat. No. 4,950,913 describes a unit designed to determine when the motor is not running. The unit detects the battery being discharged and this condition starts a timer which will eventually disconnect the radio or other connected equipment at the end of a pre-set time. If the battery is weak, a separate voltage detector will override the timer and shut the radio off. This condition will continue until the vehicle is started, thereby activating a vibration detector which will reset the system.
With memory intensive communication systems, a more serious problem arises that U.S. Pat. No. 4,950,913 cannot solve. Memory intensive systems, normally, need the data saved prior to shutdown so this data is not lost. When the unit of U.S. Pat. No. 4,950,913 disconnects to a memory intensive system prior to any data save routine, the data or information is lost. This problem can occur for a number of reasons. One reason is that the unit of U.S. Pat. No. 4,950,913 can shut the system down. Another reason is that there could be a brief power interruption which can reset the unit. Or, the battery may be weak and the input voltage can fall below the regulator's 10 volt threshold. This voltage failure will cause the regulator to draw excessive current in attempt to keep power in the system. Like each mentioned direct or indirect shutdowns, the results are disastrous for the user of the equipment because the data in the memory intensive electronics is lost.
Accordingly, a device is needed to delay shutdown so a memory save can be performed. This device should not only include many of the features previously set forth in U.S. Pat. No. 4,950,913, but also include an emergency override feature to protect memory intensive communication systems.